Charcoal Application to Arable Soil: Effects on CO₂ Emissions

Abstract

Activated carbon and commercial household charcoal were added to soil in a 36-day incubation study at 20 °C measuring carbon dioxide evolution. The black carbon materials were found to decompose slowly, releasing between 1.4% and 0.8% of their carbon content per year, respectively. The main experiment tested whether the black carbon additions to soil (2% and 4% by mass) affected decomposition of selected substrates in soil, both respiration dynamics and total respiration. The results indicated that the black carbon materials tested had no effect on total respiration from added glucose. However, decomposition rates of amylose, xylan, casein, and ryegrass were reduced in soil with addition of activated carbon but were not significantly affected by household charcoal. A larger surface area of activated carbon than that of household charcoal, and thus a greater adsorption capacity for organic compounds and exo-enzymes required to break down water-insoluble substrates, may explain the results.

Keywords:

• Biochar
• black carbon
• carbon sequestration
• decomposition
• microbial respiration
• soil carbon

Acknowledgments

We thank S. Järås and K. Sjöström at the Royal Institute of Technology (KTH) in Stockholm for their advice and acknowledge the Swedish Research Council for Environment, Agricultural Sciences, and Spatial Planning (FORMAS) for financial support.